Damian Gore

Archaeometrists use a variety of analytical methods to determine trace elements in ancient Greek silver coins, for provenance studies, understanding social and technological change, and authentication. One analytical problem which is little documented is understanding the horizontal spatial heteroge-neity of coin elemental composition in micro-sampled areas, which are usually assumed to be uniform. This study analysed ten ancient Greek coins representative of silver circulating in the Aegean region in the sixth to third centuries BC. Scanning electron microscopy with energy disper-sive spectrometry was used to map the spatial distribution of elements on coins that were abraded to remove the patina. Time of flight-secondary ion mass spectrometry was then conducted on selected coins, mapping an area ∼100 × 100 µm and depth profiling from 0 to 10 µm. These data revealed the three-dimensional elemental complexity of the coins, in particular, the heterogeneity both in the patina and beneath it. These data will guide future authentication and provenance studies of larger sample sets of ancient Greek coins including the use of line scanning for laser ablation inductively coupled plasma mass spectrometry data collection rather than spot analyses, and non-destructive analytical techniques such as X-ray fluorescence spectrometry.

The non-destructive nature of X-ray fluorescence (XRF) spectrometers is a principal reason for an increase in their use in archaeological science over the last 15 years, especially for analysing museum-curated artefacts and in situ site fabrics. Here, we show that low power XRF spectrometry can be detrimental for luminescence dating (surface applications such as mud-wasp nest dating in particular). We investigated the effects of irradiation by X-rays emitted from handheld and benchtop spectrometers on optically stimulated luminescence (OSL) signals. Measurements were taken using a portable OSL (pOSL) unit on the following unprepared archaeological materials: sedimentary quartz grains, pottery, a mud-wasp nest, stone tools and a rock flake with anthropogenically applied pigment and natural pigmentation (iron oxides). We observed an increase in luminescence compared to initial background counts for all materials tested, which could lead to overestimation of age determinations in some situations. Our experiment provides a reminder of the potential effects of X-ray radiation, and the need for thorough documentation of all recording and analytical techniques applied to archaeological materials.

Potentially toxic substances in electrical and electronic equipment are increasingly regulated, yet there is little guidance regarding appropriate sample preparation and analysis for compliance testing. Printed circuit boards are likely to contain regulated substances. Unfortunately, they are very difficult to break into homogeneous components of a mass allowing ready analysis by X-ray fluorescence (XRF) spectrometry, instrumental neutron activation analysis or dissolution-based techniques such as inductively coupled plasma, yet they must be analyzed despite this heterogeneity. Analysis of unprepared samples of circuit board using microspot, hand-held, benchtop and polarizing XRF spectrometers results in unacceptable analytical precision. Shredding samples to < 0.5 mm improves analytical precision sufficientlyfor RoHS compliance screening. To improve analytical precision further, additional sample preparation by fine shredding or milling is required. Milling for 90 s using a puck and ring mill reduces mean particle size to < 90 microm, which is sufficiently fine for XRF analyses or acid dissolution. Sample loss during milling means that fine shredding is probably an optimal form of sample preparation.

Transportable energy dispersive X-ray fluorescence (XRF) spectrometers allow the elemental compositions of coins to be measured at collections, enhancing security while maximising access to historically important material. We assessed 10 silver coins, using five XRF spectrometers. We found no systematic differences between analyses using Mo-and Rh-anode tubes, and no substantial advantage using He flush over air for elements heavier than Ti. Higher voltage X-ray tubes enhanced analytical precision. Understanding patina composition made a numerical correction possible, allowing an approximation of the underlying coin metal with good results for metals including Cu, Ag, Au, Pb and Bi.

The remediation of the Thala Valley landfill, Casey Station, East Antarctica, is part of efforts to clean-up contaminated sites associated with the Australian Antarctic Program. These sites, ranging from abandoned rubbish dumps to fuel spills, are contaminated principally with metals and petroleum hydrocarbons. Remediation success depends on accurate, cost-effective and timely--fit-for-purpose--chemical analysis of soil and water samples from the site, which is required to guide excavation, the in situ or off-site treatment and disposal of contaminated material, and to validate satisfactory remediation. Owing to the remote location of Antarctica, it is necessary to carry out chemical analyses on-site. Waste and soil contaminated with Pb, Zn, Cd, and Cu were excavated from Thala Valley for removal to Australia, treatment and disposal. Analysis of total metal concentrations in soil was performed at Casey Station with a transportable energy dispersive X-ray fluorescence (EDXRF) spectrometer. Soil samples were prepared using a simple size-fractionation method to expedite sample throughput. A method for assessing contaminant mobility in solid waste (toxicity characteristic leaching procedure, TCLP) was also used to characterise soil. Although this was more labour-intensive and time-consuming than the total metals analysis, it was of great utility because leachable metals were often significant determinants in the assessment of contaminated soil. The combined data helped managers during remediation, directing excavation and allowing waste to be classified for treatment and disposal before its return to Australia.

Controlled Release Nutrient sources assist in the bioremediation of hydrocarbon spills by stimulating microbial activity. However, freeze–thaw activity might result in splitting of fertilizer pellets with the uncontrolled release of nutrients. We examined the role of freeze–thaw and three moisture levels on nutrient release from MaxBac®, a nitrogen and phosphorus-based fertilizer encapsulated by an organic resin. We found that moisture

The retreat of the East Antarctic ice sheet at the end of the last glacial period has been attributed to both sea-level rise and warming of the ocean at the margin of the ice sheet, but it has been challenging to test these hypotheses. Given the lack of constraints on the timing of retreat, it has been difficult to evaluate whether the East Antarctic ice sheet contributed to meltwater pulse 1a, an abrupt sea-level rise of approximately 20m that occurred about 14,700 years ago. Here we use terrestrial exposure ages and marine sedimentological analyses to show that ice retreat in Mac. Robertson Land, East Antarctica, initiated about 14,000 years ago, became widespread about 12,000 years ago, and was completed by about 7,000 years ago. We use two models of different complexities to assess the forcing of the retreat. Our simulations suggest that, although the initial stage of retreat may have been forced by sea-level rise, the majority of the ice loss resulted from ocean warming at the onset of the Holocene epoch. In light of our age model we conclude that the East Antarctic ice sheet is unlikely to have been the source of meltwater pulse 1a, and, on the basis of our simulations, suggest that Antarctic ice sheets made an insignificant contribution to eustatic sea-level rise at this time.

Past changes in East Antarctic Ice Sheet (EAIS) volume are poorly known and difficult to measure, yet are critical for predicting the response of the ice sheet to modern climate change. In particular, it is important to identify the sources of sea-level rise since the Last Glacial Maximum (LGM), and ascertain the present-day stability of the world's largest ice sheet. We present altitudinal transects of 10Be and 26Al exposure ages across the Framnes Mountains in Mac. Robertson Land that allow the magnitude and timing of EAIS retreat to be quantified. Our data show that the coastal EAIS thinned by at most 350 m in this region during the past 13 k.y. This reduction in ice-sheet volume occurred over a ˜5 k.y. period, and the present ice-sheet profile was attained ca. 7 ka, in contrast to the West Antarctic Ice Sheet, which continues to retreat today. Combined with regional offshore and terrestrial geologic evidence, our data suggest that the reduction in EAIS volume since the LGM was smaller than that indicated by contemporary ice-sheet models and added little meltwater to the global oceans. Stability of the ice margin since the middle Holocene provides support for the hypothesis that EAIS volume changes are controlled by growth and decay of Northern Hemisphere ice sheets and associated global sea-level changes.